rust: lsm: replace core::mem::zeroed with pin_init::zeroed

All types in `bindings` implement `Zeroable` if they can, so use
`pin_init::zeroed` instead of relying on `unsafe` code.

If this ends up not compiling in the future, something in bindgen or on
the C side changed and is most likely incorrect.

Link: https://lore.kernel.org/r/20250814093046.2071971-8-lossin@kernel.org
Link: https://github.com/Rust-for-Linux/linux/issues/1189
Signed-off-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Nils Lehnen <nils.lehnen@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
[PM: subject tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>

rust/kernel/security.rs

@@ -62,8 +62,7 @@ impl SecurityCtx {
     /// Get the security context given its id.
     #[inline]
     pub fn from_secid(secid: u32) -> Result<Self> {
-        // SAFETY: `struct lsm_context` can be initialized to all zeros.
-        let mut ctx: bindings::lsm_context = unsafe { core::mem::zeroed() };
+        let mut ctx: bindings::lsm_context = pin_init::zeroed();
 
         // SAFETY: Just a C FFI call. The pointer is valid for writes.
         to_result(unsafe { bindings::security_secid_to_secctx(secid, &mut ctx) })?;